The present invention relates to adjusting mechanism for automobile headlamps or the like, and more particularly relates to an improved assembly and construction of such mechanisms.
Particularly successful modern adjusting mechanism for vehicle headlamps are described for example in U.S. Pat. Nos. 4,674,018 and 4,893,219. In the described mechanisms, an adjusting screw is coupled to the headlamp housing and extends into a gear box or adjustment mechanism. The adjusting screw is operatively coupled to an adjusting drive shaft which is operated by conventional hand tools, by means of a pair of mitered gears and a threaded connection. The gear members can be assembled and sealed within the integral gear housing, while allowing the drive shaft and adjusting screw components to be assembled at a later time with a variety of shaft and screw lengths as required for different model automobiles. Preferably, the adjusting screw is prevented from rotating so that its motion is limited to linear translation to pivot the headlamp housing to a desired orientation. In order to prevent rotation of the adjusting screw, the end of the screw can be provided with radial ears which are received within slots formed in the headlamp housing, although in service the ears are subject to failure under the stress of resisting rotational torque. An alternative arrangement has been proposed in U.S. Pat. No. 4,796,494 in which the adjusting screw is provided with an elongate flat which slidably engages a projection of the drive gear to prevent the adjusting screw from rotating. The drive gear thus requires complex fabrication to produce the necessary configuration for cooperating with the flat on the adjusting screw. Also, the metal-to-metal engagement of this design is undesirable as it can produce galling or electrolytic corrosion. These disadvantages are eliminated by adjustment mechanisms in accordance with the present invention.